Non-metallic conductor



g- 2, 1955 L. c. WOLCCTT 2,714,623

NON-METALLIC CONDUCTOR Filed March 9, 1950 3 Sheets-Sheet l BRA/DEB.THBfAD Aug. 2, 1955 L. c. WOLCOTT NON-METALLIC CONDUCTOR 3 Sheets-Sheet2 Filed March 9, 1950 7K W E m E K n m m a. Li Lb \M \HMH. 4 a y NU. HQ,Q, Q g gw m; m w I Q? \m w o g TI: m KQ mfim 3 \N @N \mw/ 3 j llxlwll fk1 Aug. 2, 1955 1.. c. WOLCOTT 2,714,523

NON-METALLIC CONDUCTOR Filed March 9, 1950 3 Sheets-Sheet 3 INVfNTO/Z[[Sl/f C. 11/016017 7%44: M y 524 1 ms ATTOHNHJ a 1 .i v H4 62 EJ liatentecl Aug 2, .95;;

Non-Marianne eortntlcron Leslie C. Wolcott, iiarren, Uhio, assignor toGeneral Motors Corporation, iBetrait, Mich, a corporation of DelawareApplication March 9, E59, Serial No. 148,595

3 Qlaims. (Cl. N l-12o) This invention relates to non-metallicconductors and more particularly to spark plug cables having nonmetalliccores. A conductor of this type is desirable since it has a uniformitydistributed resistance of such value as to suppress interference byoperation of the ignition apparatus of an automobile with radio andtelevision apparatuses.

An object of the invention is to provide a cable having a non-metallicconductor of small and uniform diameter and which has good tensilestrength. in the disclosed embodiment of this invention this object isaccomplished by bunching together parallel threads and braiding thereona covering of other threads while the parallel threads are maintainedunder uniform tension. The braided core is impregnated with suitablecarbonaceous material, such as graphite and is dried, and a coating isapplied thereto in order to stiffen the core to facilitate threading itthrough an extruder head and to provide a bond between the braided coreand the insulation which is extruded around it.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being bad to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Fig. l is a view of a piece of the braided core;

Fig. 2 is a diagram of the apparatus forming the braided core shown inFig. 1;

Fig. 3 is a View showing on a large scale a fragment of athread-tensioning device;

Fig. 4 is a view in the direction of arrow 4 of Pig. 3;

Fig. 5 is a sectional view on line 5-5 of Fig. 3, showing the relationof the teeth of the tensioning combs before tension is applied;

Fig. 6 is a view similar to Fig. 5 show" g the relation of thetensioning combs after tension is applied to a thread;

Fig. 7 is a diagram of the apparatus for impregnating the braided coreand for applying latex thereto;

Fig. 8 is a diagram of the take-up apparatus used in connection with theapparatus shown in Fig. 7;

Fig. 9 is a side view of a capstan included in the appa ratus shown inFig. 7;

Fig. 10 is a longitudinal sectional view of one of the nipples dd drawnto a larger scale than Fig. 7;

Fig. 11 is a fragmentary perspective View of a portion of the finishedcable.

Referring to 2, a plurality of threads 2% are pulled from spools 21supported by a table and are passed through eyes 23, tensioning deviceseyes 25 and are bunched together by passing them through an eye 26 toprovide a core 27. The core 27 is passed around a power driven capstan23 and then secured to a power driven take-up reel 29. While the core 27passes upwardly, a covering of braided thread 3 is applied thereto by abraider which is represented diagrammatically by a plu rality of spools31 from each of which a thread a is drawn while the spools are movedaround the core and are used to intertwine in a manner well known to theart of braiding.

The threads 20 should be of material which is tough and resilient andhas sufficient tensile strength and which, comprises small individualfibers so as to present a relatively large area for coating by the coreimpregnating material. Linen threads are preferred since they providethe required strength for a small diameter of core. For example, ninelinen threads each 30 lea, will make a core approximately .053 indiameter. Various materials, such as cotton, linen, rayon, glass orcombinations of these materials, could be used, depending upon thetensile strength required and the temperature to which the material isexposed during the curing process.

The braid threads Iilla can be of any of the materials usable as thecore threads 20. The braid threads should be small in diameter so as notto increase substantially the diameter of the core. Rayon threads of 300denier size are satisfactory.

Each of the tensioning devices 24 is a conventional form of threadtensioning device. As shown diagrammatically in Figs. 3 and 4, the fixedcomb member 33 having tines 35 cooperates with a movable comb member 34having tines 36 and pivotally supported by rod 37 fixed to the comb 33.Eyes 23 and 25 direct each linen strand 2'?) between the comb tines andsubstantially at right angles thereto. To apply tension to the threadthe comb 34 is adjusted to the comb 33 in order to bring the tines 36closer to the tines 35 as shown in Fig. 6, so that the thread 2iintertwines the tines. Each of the tensioning devices 2 is adjusted sothat the tension on each of the threads between the tensioning devicesand the capstan will be substantially uniform. As shown diagrammaticallyin Fig. 4, the tension is adjusted by adding or removing weights 38supported by a plate 39 attached to a cord 49 passing around a pulleyand attached to an arm 42 connected with comb 34. Comb 33 is integralwith a fixed supporting bracket 43. The tension on each thread can bedetermined by attaching thereto a scale which, on being pulled to drawthe thread through the tensioning device, will indicate the amount oftension. The uniformity of thread tension is desirable so that, when thetension is relieved during a subsequent step, the threads will contractequally and no threads will form a bulge or loop.

The braided core is impregnated with carbonaceous material by passing itthrough a solution comprising preferably, by weight, four parts water,one part aquadag and one-tenths of one percent of a Wetting agent,preferably dioctyl sodium sulfosuccinate known to the trade as AerosolO. T.

Aquadag is understood to be a suspension of graphite with a bindercomprising starchy material and protein material which makes it adhere.

The impregnating and drying apparatus is shown diagrammatically in Fig.7 in which the braided core is indicated by a single line 50. Therefore,numeral 50 in Fig. 1 indicates the assembly of core and braid. Thebraided core 50 is unwound from the reel 29 (Figs. 2 and 8) and passes afew turns around a capstan 51, down into a tank T1 containing theaquadag solution, around a pulley 52, up into an oven 0, around a pulley53, down through the bottom of the oven, around a capstan 54 a fewturns, down into tank T1 around a pulley 55, up into the oven, around apulley 56, down through the bottom of the oven, around a capstan 57 afew turns, down into tank T1, around a pulley 58,

up into the oven, around a pulley 59, around pulleys 66-67 all in theoven, down through the bottom the oven, around a capstan 68 around aninsulated brass pulley 69, again around the capstan 68, down into a tankT2 containing the coating solution, around a pulley 74, up into theoven, around a pulley 75, down through: the bottom of the oven, aroundan insulated pulley 76, around a dual capstan 77 a few turns and then toa take-up reel '78 (Fig. 8). Capstan 77 comprises two grooved pulleys,one being driven and the other idling.

A motor 79 (Fig. 8) drives, through speed reducing V-belt drives(comprising pulley 30, belt 89a and pulley 81), a shaft 82 connected byspeed reducing gears 83, 84 with a shaft 85 connected by sprocket 86,chain 87 and sprocket 88 with a shaft 89 connected with the dual capstan77. Sprocket 90, chain 91, sprocket 92 and a friction, slipping clutch94 connects the shaft 89 with a shaft 95. Sprocket 93 takes up slack inchain 9.1. Shaft 95 drives a disc 96 carrying pins 97 which are receivedby holes in the hub of reel 78 when it is mounted upon shaft 95. Atraverse mechanism (not shown) driven by shaft 95 guides core 50 in evenlayers upon reel 78.

A brake drum 98 journaled on shaft 95 carries pins 99 which are receivedby holes in the hub of reel 29 when mounted on shaft 95. Drum 98 isengaged by a leather strap anchored at 101 to apply a light friction tothe drum 98. Strap 101 is attached to a rod 102 which passes through afixed bar 193 and receives a nut 155 which confines a spring 104 undercompres sion. By turning the nut 105, the friction applied by the strap101 to the drum 98 is so adjusted as to obtain the frictional dragsuflicient to take up slack in core 50 between the reel 29 and thecapstan 51 and also to make the capstans pull evenly and give a uniformlow tension.

Capstans 51, 54, 57 and 68 are connected with a shaft 110 (Fig. 7)driven from shaft 89 by a chain drive comprising sprocket 111, chain111:: and sprocket 11111. Capstans 68 and 77 (driven by motor 79) havethe same peripheral speed. Capstans 51, 54 and 57 are larger in diameterthan capstans 65 and 77, and are alike. Referring to Fig. 9, which showscapstan 51, each of these capstans 51, 54 and 57 have a conicalperiphery 112 at 10 degree taper between flanges 113 and 114. Theperiphery 112 is chrome-plated and polished. The turns of the core 55received by the periphery 112 tend to move toward flange 113 and lie inan even layer. Since the diameter of these peripheries is greater thanthe diameter of the core-engaging surfaces of capstans 68 and 77 thereis slippage between the core 59 and these peripheries. The capstans 51,54 and 57 cooperate in a manner such that there is no appreciablestretch in the core 54) as it passes down into' the tank T1 and up intothe oven 0. These capstans impart to the core 50 only the amount oftraction required to take up the slack in the core. Since the core 50 isnot being stretched while passing through the tank T1 and the oven, itwill absorb the maximum amount of aquadag.

Pulley 69 is insulated electrically from pulley 68, and a resistancemeasuring instrument is connected in a circuit which includes thesepulleys and a current source so that amount of resistance in a portionof the core 50 can be measured in order to determine whether the desiredresistance is being obtained.

A satisfactory coating solution in the tank T2 consists of:

Parts Neoprene latex 740 Acetylene black 100 Marasperse C. B 60 Igepal C2 Marasperse C. B. is used as a dispersing agent for carbon blacks andits chemical composition is about 91% sodium lignosulfonate and about 9%inorganic matter.

Igepal C., which possesses good wetting, emulsifying and detergencyproperties, in an alkyl aryl polyethylene glycol made from thecondensation of alkyl phenol with ethylene-oxide. The kind of neoprenelatex which is desirable to use as a coating is one which does notcoagulate when unusual amounts of acetylene black are mixed with it inorder to increase the electrical conductivity of the coating. Neoprenelatex is desirable because it is not affected by lubricating oil whichmay be present at the guider tip of the extruder head Which is used toextrude a jacket of insulation about the coated core. The neoprene latexis compounded with known vulcanizing agents so that curing will takeplace in the oven 0. Each of the Wipers 71 and 74 comprises, as shown inFig. 10, a wiper nipple which a clamping band 121 attaches to a pipe 122supported by a fixed plate 123. The function of the nipple 120 is toWipe off the excess coating before baking the coating which remains.

The material Wound on the spool 78 is unwound therefrom, passed throughan extruder which places a first sheath of insulation 125 (Fig. ll)around the coated core. The sheathed core passes from the extruderthrough cold water in order to set up the insulating sheath so that theuncured sheath will not be deformed when the sheathed core is wound on atake-up reel. From the take-up reel the sheathed core is passed througha second extruder which applies sheath 126 (Fig. l1); and the cable islaid in a pan and both sheaths 125 and 126 are vulcanized simultaneouslyby the batch method in a steam vulcanizer.

The insulation material may be any suitable elastomer.

For the sheath 125, rubber is satisfactory; and for the sheath 126,neoprene is preferred because it resists attack by lubricating oil andgasoline. The core coating of material such as neoprene latex has thefollowing functions: (1) It stiffens the core to facilitate threading itthrough the guider tube of the extruder head used in applying the firstsheath 125. (2) it binds the braid threads together and therebypractically eliminates the tendency of the braid to sleeve back on theparallel threads and bind in the guider tube of the first extruder head.Because sleeving back is avoided, the diameter of the guider tube can besmaller than otherwise whereby it fits the core more closely to providefor centering it more accurately with the extruder die and thus with thesheath extruded around it. (3) It promotes adhesion of the first sheath125 to the core so that the first sheath does not slip on the core whenpassing through the second extruder which applies the sheath 126. if theadhesion were not sufficient, the first sheath 125 might slip back onthe core and bind in the guider tube of the second extruder. (4) Bypromoting adhesion the presence of air pockets and consequently coronais minimized. (5) It does not cause leaching out of the impregnatinggraphite; but, on the contrary, materially improves conductivity byreason of the amount of acetylene black it can carry withoutcoagulating.

The oven 0 is heated with direct fired gas. Since the same oven is usedfor drying the aquadag and for curirig the latex, the passes of the corefor drying the aquadag are longer than the passes for curing the latex.After each of the first and second passes through the aquadag there is asingle up and down pass in the oven for partially drying the aquadagbefore a subsequent pass through the aquadag. After the third passthrough the aquadag, there are a plurality of passes up and down in theoven to cause the aquadag to be thoroughly dried before applying thelatex. For satisfactory results the top temperature of the oven can bein the range of 250 to 275 F. For a'particular oven, the satisfactorycore speed is 18 feet per minute when top temperature is 250 F and is 20feet per minute, when top temperature is 275 F. At speeds faster thanthose specified for those temperatures, the aquadag is not driedproperly. At temperatures above 275 F, the binders tend to burn out ofthe aquadag and it flakes oit so much that the required resistivity isnot obtained.

In the claims which follow the term rubber latex means any latex of arubber-like elastomer, such as neoprene latex; and the term rubbersheath includes a sheath of any rubber-like elastomer.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. An electrically conducting cable comprising a nonmetallic fibrouscore formed of a plurality of straight parallel threads covered by asheath of braided threads, said core being impregnated with comminutednonmetallic conducting material and coated with rubber latex, the coatedcore being encased in a rubber sheath which surrounds the coatedsurface, the latex providing a bond between the core and sheath.

2. An electrically conducting cable comprising a nonmetallic fibrouscore which includes substantially parallel threads encased in a sheathof braided threads, said core being impregnated with cornminutedconducting material and encased by an insulating sheath and having,intermediate the core and sheath, an intermediate layer of bondingmaterial.

3. An electrically conducting cable comprising a nonmetallic fibrouscore which includes substantially parallel linen threads encased in asheath of braided rayon threads and impregnated with comrninutedgraphite and coated with rubber latex and encased in a rubber sheathbonded to the core by virtue of the latex coating.

References Cited in the file of this patent UNITED STATES PATENTS

